any plugin that moderates new users in MU that really works?

Hi: The issue of spam has gotten us into trouble. I have been looking for a looong time for a ‘new user moderation plugin’ to use in our site running WordPress MU (latest version) and Buddypress (latest version). the few we tested don’t work. Anyone knows of something that addresses the following?
(1) anyone can register, including upload their avatar just as it is right now.
(2) Their registration will remain in a place where only Admin can see, after receiving an alert.
(3) Admin clicks a button to authorize the legitimate registrants and may send the IP address of unwanted into a pool of BAN.